To deal with weight reduction, miniaturization, high speed, multifunction, and high performance trends in electronic devices, forming a plurality of wiring layers on circuit boards such as printed circuit boards (PCB), known as multilayer board technologies have been researched. Moreover, a technology to equip electronic components such as active elements or passive elements on the multilayer circuit board has been researched.
Meanwhile, due to multifunction and the high performance of application processors connected to the multilayer circuit board, the heat-conducting requirements have significantly grown.